# How best to put together a circuit with 30 dc motors controlled by one switch?

My most straightforward idea is just to wire 30 motors, 30 9v batteries, and a switch in series, but I was wondering how I can use a single power source rather than 30 batteries, and also if wiring all the motors in parallel has advantages to wiring them in series even if I just intend to turn them all on or all off? Thanks.

So you'd consider a 270V DC source to wire them all in series? Wow. How much current for each motor?

CrossRoads: So you'd consider a 270V DC source to wire them all in series? Wow. How much current for each motor?

I don't have any data on the current of the 12v motor I tested with, so all I know is that I like how it runs on a 9v battery. Admittedly, I had a feeling something was off too if I was planning to use a 270v source, but my understanding of circuitry doesn't go beyond what I learned in physics.

Now that I think about it, however, I remember reading that one advantage of parallel wiring is that the resistance remains constant, so does that mean I can just wire all 30 motors in parallel and hook it up to a single 9v battery? That can't be right, can it?

You can, will just need large current capability.
Say each motor needs 100mA - then 30 motors means 3A supply.
Don’t forget a diode across each motor as well.

CrossRoads: You can, will just need large current capability. Say each motor needs 100mA - then 30 motors means 3A supply. Don't forget a diode across each motor as well.

Great! Thanks for the schematic. Can I wire up 30 servo motors in the same way?

Yes, sort of - Servos need power & gnd each, but there is a seperate control line with a PWM type signal from the Arduino. Not sure you can drive 30 servos with 1 signal, need to check the servo & its control needs.

CrossRoads: Yes, sort of - Servos need power & gnd each, but there is a seperate control line with a PWM type signal from the Arduino. Not sure you can drive 30 servos with 1 signal, need to check the servo & its control needs.

Thanks! That helps. I won't actually be driving all the servos with one signal. I plan to have the signal line of each servo connected to a different channel on an arduino mega, and I'll be controlling the 30 servos individually. Thanks again for the advice.

If you want all the motors to exhibit the same torque, series connection can be used (you get a sort of differential effect), but if you want the same speed you need to wire in parallel (which is saner anyway, no lethal voltages involved).

What size of motor are we talking about, the small 9V PP3-sized batteries cannot power any but the tiniest motors without overloading. A decent 12V SLA would be an obvious choice for multiple motors.

What are you wanting to power? Without sizing the motors for the load(s) involved you are likely to be disappointed.

MarkT: What size of motor are we talking about, the small 9V PP3-sized batteries cannot power any but the tiniest motors without overloading. A decent 12V SLA would be an obvious choice for multiple motors.

What are you wanting to power? Without sizing the motors for the load(s) involved you are likely to be disappointed.

I can't find any motor specs beyond what is posted on the Amazon listing (http://www.amazon.com/Amico-6000RPM-Diameter-Magnetic-Hobby/dp/B008595SC8/ref=sr_1_1?ie=UTF8&qid=1389137238&sr=8-1), and I intend for the motor to just move a light load (each motor attached to a 2" wheel to shoot a light 1" ball forward). Since the motors will never be simultaneously shooting balls, I think I can use the total no-load current for the motors. The motors I'm interested in would need about 2-3 A total for 30 motors (for just simultaneous no-load spinning), so I agree a PP3 battery may be just insufficient. So if you can recommend a different type of 9v battery that's also inexpensive, I'd appreciate it. Thanks!

so I agree a PP3 battery may be just insufficient.

Just insufficient! Vastly insufficient more like. If you are looking to get 3A out of a battery then you need LiPo battery. Even so it won't last long.

Grumpy_Mike: Just insufficient! Vastly insufficient more like. If you are looking to get 3A out of a battery then you need LiPo battery. Even so it won't last long.

Lol. I thought I saw some specs online that gave the max current of a duracell 9V pp3 battery as 2A, but I see now that I was misinformed. So what type of power source would be most reliable/recommended for my purposes? Thanks.

It just occurred to me now, why don't I just wire up as many 9v pp3 batteries as I need in parallel? Is there some significant disadvantage to doing that?

EDIT: And then I realized, I would be shorting everything unless I include a switch in series with every battery, right? lol